1. Field of the Invention
The invention relates to a transmission, especially for a motor vehicle. More particularly, the invention relates to a transmission that has a plurality of sets of gears forming transmission ratio steps, wherein the gear sets are each formed by one gear that is non-rotatably carried on one shaft and by an idler gear connectable with another shaft, whereby transmission ratio steps can be selected, and in which an idler gear is connected with its associated shaft by an output element that is part of a final output mechanism that is actuated by a final actuation mechanism, whereby the selection sequence of the transmission ratio steps is not established in the final actuation mechanism.
2. Description of the Related Art
A final output element is the element that is moved in order to set a transmission ratio condition. That is, it is the element, such as, for example, a coupling sleeve, that produces the connection between two power transmission means. The final output element is part of the final output mechanism, which includes adjacent to the coupling sleeve a shift fork, for example, which is connected with the coupling sleeve and is movable by a shift finger that can be operatively connected with it so that the coupling sleeve is moved to engage or disengage a transmission ratio step. The shift finger is part of the final actuation mechanism that actuates the final output mechanism. The entire kinematic chain between the shift or selection actuation and the final output mechanism is designated as the final actuation mechanism.
In state-of-the-art transmissions, the interaction between the final output mechanism and the final actuation mechanism takes place in such a way that engagement of a transmission ratio step can only take place when no other transmission ratio step is engaged. In order to engage a transmission ratio step, all other transmission ratio steps must previously be positively disengaged. The shift fork jaws, with which the shift finger can be connected in order to shift the coupling sleeve with the respective shift fork, are constructed such that the shift finger can only be connected with another shift fork if the coupling sleeve with whose shift fork it is then connected is in the neutral position. In reference to a known manual transmission with an H-shift pattern, that manifests itself in that a selection movement of the gear shift lever from one shift passageway into another can occur only in the neutral passageway, whereby during a shift lever movement from one shift passageway into the neutral passageway the same transmission ratio step that was engaged at the time is disengaged. Moreover, the transmission ratio steps that can be shifted by the same coupling sleeve cannot be selected simultaneously. Consequently, it is necessary in a shift procedure to disengage a previous transmission ratio step, to conduct a selection movement, and then to engage a new transmission ratio step. During that time, the flow of torque is interrupted by a disengaged drive clutch, because the drive branch must be load-free. In the event that selection of a shift passageway is necessary, the shift process turns out to be relatively long, which can be disturbing and relevant to safety, especially with automated shift transmissions with tractive force interruption, for example during passing, turning, and the like.
Especially with load-shiftable transmissions, in which the transmission ratio steps form groups or are assembled into groups between which tractive-force-interruption-free load shifts can be conducted, for example in which the transmission ratio steps are included in different parallel power branches, the various output elements are arranged with a friction clutch so that a continuous change of torque from one branch to another branch can be brought about by an actuation of a friction clutch during gradual changes. Configurations of the connection of the final output mechanism and the final actuation mechanism have become known, which permit engaging one transmission ratio step without having to disengage another transmission ratio step that may already have been engaged. In that way, it is possible to engage several transmission ratio steps simultaneously in several power branches using a single final actuation mechanism by first selecting one transmission ratio step in one branch, then allowing the shift finger to connect with other shift forks—without having to disengage the relevant transmission ratio step—in order to select further transmission ratio steps. In that connection, published German application DE 100 20 821 A1 owned by the applicant is relevant, the contents of which are incorporated in the disclosure of the present application.
Usually two groups of transmission ratio steps are formed, whereby successive transmission ratio steps belong to different groups with respect to the division of their gear ratios. For example, one transmission includes one reverse gear and six forward gears, one group includes gears 1, 3, and 5 and the other groups gears R, 2, 4, and 6.
Such a transmission offers the possibility of selecting one transmission ratio step using the friction clutch in the power branch included in the torque flow, and then engaging in another—still open branch—the transmission ratio step into which a shift is subsequently to take place by diverting the torque flow to the relevant branch. During acceleration, for example, it is possible to shift into fourth gear in one branch during an upshift while in the closed power branch the third gear is engaged. In the event that now suddenly nonetheless a downshift into second gear is to take place, the fourth gear must first be disengaged and then the second gear must be engaged, which in particular causes a very great loss of time if the second and fourth gears must be shifted by different coupling sleeves.
Furthermore, a negative situation can arise for a transmission shift in which, with an open power branch, more than one transmission ratio step is engaged, which represents a very great safety risk because as soon as that branch is tied into the torque flow, several transmission ratio steps with different transmission ratios become operative, which can lead to the transmission becoming blocked or even destroyed.
Additionally, so-called controller drum transmissions have become known, in which the final output mechanisms of the transmission ratio steps are actuated using a rotatable controller drum. For example, link-like grooves are incorporated in the controller drum, which extend circumferentially as well as axially on the surface of the cylindrical controller drum, so that by rotating the controller drum about its longitudinal axis shift forks, which are connected kinematically with the controller drum by means of sliding elements in the grooves, undergo movement in the axial direction of the controller drum. The shift sequence of the transmission ratio steps with reference to the rotation of the selector shaft is established by the shapes of the grooves. By appropriate configuration of the grooves, controller drum transmissions of that type make possible an overlapping disengagement of a previous transmission ratio step and engagement of a new transmission ratio step, whereby a certain time advantage is achieved during a shift process, and consequently the duration of the tractive force interruption can be reduced. Nonetheless, shifts are only possible sequentially. For example, a direct shift from first gear into third gear is just as impossible as a direct downshift from fifth gear into first gear.
An object of the invention is to provide a transmission, for example an automated shift transmission, a load-shifting transmission, a double-clutch transmission, and the like, with transmission ratio steps distributed between at least two different shafts, in which the shift sequence of the transmission ratio steps is not established in the final actuation mechanism, in which shift times are substantially reduced, and safety is substantially improved. The transmission should furthermore have a simple design, with as few components as possible, and be simple to operate without additional safety measures.